Wafer prober for testing in-wafer photonic integrated circuits

ABSTRACT

The invention relates to a wafer prober including an optical waveguide, the optical waveguide having a first optical coupling end segment with a first optical coupling surface being devoid of cladding. The first optical coupling end segment being configured to provide an adiabatic optical coupling to a second optical coupling end segment of a second optical waveguide of a photonic integrated circuit on a semiconductor wafer when the optical waveguide is aligned with respect to the semiconductor wafer according to a set of alignment requirements. The second optical coupling end segment having a second optical coupling surface that is devoid of cladding. The second optical coupling surface is parallel to a wafer surface of the semiconductor wafer. An alignment system configured to align the optical waveguide with respect to the semiconductor wafer according to the set of alignment requirements.

DOMESTIC PRIORITY

This application is a continuation of the legally related U.S.application Ser. No. 14/941,959 filed Nov. 16, 2015 which is fullyincorporated herein by reference.

BACKGROUND

The present invention relates to information processing apparatus, aninformation processing methods and programs.

Modern integrated circuits can have not only discrete elements (e.g.transistors) but further comprise photonic components. Electrical testterminals of the discrete elements or of functional groups thereof areas usual located on a surface of a wafer. Such an allocation of theelectrical test terminals enables early testing of the integratedcircuits. For instance this early testing using the electrical testterminals can be performed before dicing of the wafer in order to inkout the defect dies. After the testing only the chips complying with thespecification are processed further (e.g. bonding, packaging, furthertesting, etc.). Electrical contacting is done as usual by employingelectrically conducting needles for connecting an electrical test systemwith the electrical test terminals. The same electrical test terminalscan be further used for bonding.

In contrast, operational photonic terminals used for connecting thechips to external optical waveguides of the package and test photonicterminals of the chips used for optical in-wafer testing are different.The operational photonic terminals are open only after dicing of thechips because they are allocated on sidewalls of the chips. Thusperforming optical in-wafer tests requires forming additional testphotonic terminals on a wafer surface. As usual they are implemented asan optical coupling segment of an optical waveguide of a chip, whereinthe optical coupling segment is covered by a grating enabling opticalcoupling of an external light source (e.g. a laser) to the opticalwaveguide of the chip. Forming of such a complex coupling structures onthe wafer surface requires not only additional process steps but demandsa substantial area of the wafer surface to be sacrificed for theseoptical couplings. As a result thereof a substantial area is wasted fortest structures which are not used for operation of chips after theirpackaging.

SUMMARY

The present invention provides for a wafer prober configured to providean optical coupling to compact optical coupling elements on a wafersurface, an optical wave guide configured to provide same, and a methodfor providing optical coupling to the compact optical coupling elementsof the wafer surface.

One embodiment provides for a wafer prober. The wafer prober comprisesan optical waveguide and an alignment system configured to align theoptical waveguide with respect to a semiconductor wafer according to aset of alignment requirements. The optical waveguide comprises a firstoptical coupling end segment with a first optical coupling surface beingdevoid of cladding. The first optical coupling end segment is configuredto provide an adiabatic optical coupling to a second optical couplingend segment of a second optical waveguide of a photonic integratedcircuit on the semiconductor wafer when the optical waveguide is alignedwith respect to the semiconductor wafer according to the set ofalignment requirements. The second optical coupling end segmentcomprises a second optical coupling surface being devoid of cladding,wherein the second optical coupling surface is parallel to a wafersurface of the semiconductor wafer.

The set of alignment requirements comprises: the second optical couplingsurface being parallel to and faces the first optical coupling surfaceand a geometrical plane comprising a longitudinal geometric axis ofsymmetry of a first core of the first optical coupling end segment and alongitudinal geometric axis of symmetry of a second core of the secondoptical coupling end segment being perpendicular to the wafer surface.

Another embodiment provides for a method for providing an adiabaticcoupling between a first optical coupling end segment of an opticalwaveguide and a second optical coupling end segment of a second opticalwaveguide of a photonic integrated circuit on a semiconductor wafer. Themethod comprises: aligning the optical waveguide with respect to thesemiconductor wafer according to the aforementioned set of alignmentrequirements. The first optical segment comprises a first opticalcoupling surface being devoid of cladding and the second opticalcoupling end segment comprises a second optical coupling surface beingdevoid of cladding. The second optical coupling surface is parallel to awafer surface of the semiconductor wafer.

Yet another embodiment provides for an optical waveguide. The opticalwaveguide comprises a first optical coupling end segment with a firstoptical coupling surface being devoid of cladding. The first opticalcoupling end segment is configured to provide an adiabatic opticalcoupling to a second optical coupling end segment of a second opticalwaveguide of a photonic integrated circuit on a semiconductor wafer whena second optical coupling surface of the second optical coupling endsegment is parallel to and faces the first optical coupling surface, thesecond optical coupling surface being devoid of cladding, the secondoptical coupling surface being parallel to a wafer surface of thesemiconductor wafer, and a geometrical plane comprising a longitudinalgeometric axis of symmetry of a first core of the first optical couplingend segment and a longitudinal geometric axis of symmetry of a secondcore of the second optical coupling end segment is perpendicular to thewafer surface.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following embodiments of the invention are explained in greaterdetail, by way of example only, making reference to the drawings inwhich:

FIG. 1 depicts a wafer prober; and

FIG. 2 depicts a cross-section of a wafer prober.

DETAILED DESCRIPTION

Minimization of “silicon real estate” sacrificed for test structures isan everlasting problem of the semiconductor industry. To a certainextent this problem is solved by placing the test structures in dicingstreets between dies on wafers. However, small test structures allocatedin the dicing streets do not always provide sufficient information aboutthe die performance. Direct in-wafer testing of chips before dicing canbe the only one way for inking out chips which do not comply with thespecification. This problem can be solved when testing of the chips canbe performed via bonding pads of the chips. However testing of photonicchips having optical waveguides cannot be implemented in the same way.Special optical coupling structures have to be formed on a wafer surfacein order to provide optical coupling of the optical waveguides on thewafer to the external light sources (e.g. lasers). Employing gratingstructures optically coupled to the optical waveguides enables in-wafertesting of chips comprising photonic circuits. The grating based opticalcoupling elements may have numerous disadvantages. For instance, a bigarea of the “silicon real estate” has to be sacrificed for forming thesecoupling elements. As a result thereof, the useful load of the chip areais substantially reduced, especially in a case when a lot of opticalsignals have to be coupled to and/or received from the chip. Anotherproblem related to employing of the grating based optical couplingsemerges from a need to use optical systems configured togenerate/receive optical rays compatible with the gratings. This problemwill manifest itself at most when multiple test optical couplingterminals have to be connected to an external test optical system. Sincethe chip area is very small, the need to send to and/or receive from thechip of multiple optical signals can require a sophisticated opticalmultichannel system, wherein said multiple optical signals have to sharethe same optical path (e.g. focusing and/or collecting optics).

The optical waveguide, the wafer prober comprising the opticalwaveguide, and a method of using the waveguide disclosed herein may haveadvantages, because the optical coupling is implemented between anin-wafer optical coupling end segment of the optical waveguide and anoptical coupling segment of the optical waveguide of a photonic circuiton a semiconductor wafer. The optical coupling end segment of theoptical waveguide and the optical coupling segment of the opticalwaveguide of the photonic circuit on the semiconductor wafer are compactstructures enabling parallel implementation of multiple couplingchannels to the photonic circuit. There is no need for a complexmultichannel optical system. The compactness of the optical couplingenables not only a substantial reduction of the chip area used forstructures providing optical coupling, but a combination of optical andelectrical testing because the optical coupling segments of the opticalwaveguides can be easily allocated on a wafer probe card together withneedles providing electrical coupling.

The optical waveguide comprises a first optical coupling end segmentwith a first optical coupling surface being devoid of cladding. Thefirst optical coupling end segment is configured to provide an adiabaticoptical coupling to a second optical coupling end segment of a secondoptical waveguide of a photonic integrated circuit on a semiconductorwafer when a second optical coupling surface of the second opticalcoupling end segment is parallel to and faces the first optical couplingsurface, the second optical coupling surface being devoid of cladding,the second optical coupling surface being parallel to a wafer surface ofthe semiconductor wafer, and a geometrical plane comprising alongitudinal geometric axis of symmetry of a first core of the firstoptical coupling end segment and a longitudinal geometric axis ofsymmetry of a second core of the second optical coupling end segment isperpendicular to the wafer surface.

The optical waveguide can be integrated in a wafer prober comprising analignment system configured to align the optical waveguide with respectto the semiconductor wafer according to the set of alignmentrequirements. The set of alignment requirements comprises: the secondoptical coupling surface is parallel to and faces the first opticalcoupling surface and a geometrical plane comprising a longitudinalgeometric axis of symmetry of a first core of the first optical couplingend segment and a longitudinal geometric axis of symmetry of a secondcore of the second optical coupling end segment is perpendicular to thewafer surface.

In one embodiment, the optical wave guide and the second opticalwaveguide being single mode optical waveguides. This can be ofadvantage, because employment of single mode optical waveguides iscustomary in photonic circuitry. In another embodiment, the opticalwaveguide is configured to function at a wavelength in a range of1240-1380 nm, the second waveguide is configured to function at awavelength in the range of 1240-1380 nm. Operation of the opticalwaveguides in the range of 1240-1380 nm can be advantageous because thisrange is one of the customary rages in which the optical waveguides ofsilicon based photonic chips operate.

In another embodiment, the optical waveguide is configured to functionat a wavelength in a range of 1450-1580 nm and the second opticalwaveguide is configured to function at a wavelength in the range of1450-1580 nm. Operation of the optical waveguides in the range of1450-1580 nm can be advantageous because this range is one of thecustomary rages in which the optical waveguides of silicon basedphotonic chips operate.

In another embodiment, the optical waveguide is a polymer-basedwaveguide comprising at least one of the following materials:silsesquioxane, poly-dimethylsiloxane, perfluoropolymer, acrylate,polyurethane, epoxy, and fluorinated polyimide. Such an implementationof the optical waveguide can be advantageous because it is based on aflexible optical waveguide. The flexible optical waveguide can be easilyintegrated on a wafer probe card, which can accommodate other testaccessories such as other optical waveguides and/or needles forelectrical testing.

In another embodiment, the optical waveguide is a glass waveguide. Suchan implementation of the optical waveguide can be advantageous becauseit is based on a rigid optical waveguide. The rigidity of the opticalwaveguide can enable aligning of the optical waveguide in the proximityof the wafer without the need to provide a rigid support for it. As aresult thereof the rigid optical waveguide can be allocated in betweenclosely spaced needles used for electrical testing.

In another embodiment, the second core of the optical coupling endsegment of the second optical waveguide on the semiconductor wafer has alongitudinally tapered shape. This implementation can be advantageousbecause it does not require any additional grating. Moreoverimplementation of this shape may not require any additional processsteps, i.e. the core of the optical coupling end segment and a core ofthe optical waveguide on the wafer connected to the core of the opticalcoupling end segment can be manufactured in the same process.

In another embodiment, the second core of the optical coupling endsegment of the second optical waveguide on the semiconductor wafer has alength shorter than 3 mm. For example, it can have the length of 2 mm.Such an implementation of the core of the optical coupling end segmentof the optical waveguide on the semiconductor wafer can be advantageousbecause it is compact.

In another embodiment, a cross-section of the second core at its endconnected to a core of the second optical waveguide completely coveredby cladding matches a cross-section of the core of the second opticalwaveguide completely covered by cladding and an area of a cross-sectionof the second core at its other end is bigger than 5% of an area of thecross-section of the core of the second optical waveguide completelycovered by cladding. Such an implementation of the core of the opticalcoupling end segment of the optical waveguide on the semiconductor wafercan be advantageous because it is compact.

In another embodiment, the first core of the first optical coupling endsegment of the optical waveguide (of the wafer prober) has the samecross-section throughout its length. Such an implementation of the coreof the optical coupling end segment of the optical waveguide can beadvantageous for providing adiabatic and/or compact coupling to theoptical coupling end segment of the optical waveguide on thesemiconductor wafer.

In another embodiment, a length of the first core of the first opticalcoupling end segment of the optical waveguide (of the wafer prober) islonger than a length of the second core of the second optical couplingend segment of the optical waveguide on the semiconductor wafer. Such animplementation of the cores of the optical coupling end segments of theoptical waveguides can be advantageous for providing adiabatic and/orcompact coupling to the optical coupling end segment of the opticalwaveguide on the semiconductor wafer.

In another embodiment, the set of alignment requirements comprises: thesecond optical coupling surface being in contact with the first opticalcoupling surface. This alignment requirement can be of particularadvantage when a polymer waveguide is employed. In this case theflexible optical coupling surface can provide almost perfect coverage ofthe rigid optical coupling surface. Direct contact of the first and thesecond optical coupling surfaces can improve the quality of theadiabatic optical coupling between the optical waveguide and the secondoptical waveguide, e.g. reduction of the coupling loss.

In another embodiment, the set of alignment requirements comprises: adistance between the second optical coupling surface and the firstoptical coupling surface being bigger than zero and less than 2micrometers. This alignment requirement can be of particular advantage,when the adiabatic coupling has to be provided in a contactless mode,when a contact between the first and the second optical couplingsurfaces has to be avoided, e.g. when the first and the second opticalcoupling surfaces are made of rigid materials.

In another embodiment, the wafer prober comprises means for providing ina space between the first and the second optical coupling surface amedium having a refractive index less or equal to a refractive index ofthe first core, wherein the first optical coupling end segment isconfigured to provide the adiabatic optical coupling to the secondoptical coupling end segment when the space between the first and thesecond optical coupling surface is filled with the medium. Thisembodiment can provide for a further improvement of the adiabaticcoupling, wherein a medium between the first optical coupling and thesecond coupling surface facilitates adiabatic coupling by confiningwithin it the electromagnetic radiation.

In another embodiment, the first core has first sidewalls being devoidof cladding, wherein the first sidewalls are adjacent to the firstoptical coupling surface. This embodiment can facilitate coupling of thefirst core to the second core, because in this embodiment, theelectromagnetic radiation can pass not only via the first opticalcoupling surface but via the first sidewalls.

In another embodiment, the second core has second sidewalls being devoidof cladding, wherein the second sidewalls are adjacent to the secondoptical coupling surface. This embodiment can facilitate coupling of thefirst core to the second core, because in this embodiment, theelectromagnetic radiation can pass not only via the second opticalcoupling surface but via the second sidewalls.

In another embodiment, the wafer prober further comprises means forproviding a contiguous volume of a medium filling a space between thefirst and the second optical coupling surface and covering the first andthe second sidewalls, the medium having a refractive index less or equalto a refractive index of a core of the first optical coupling endsegment, wherein the first optical coupling end segment is configured toprovide the adiabatic optical coupling to the second optical couplingend segment when the contiguous volume of the medium fills the spacebetween the first and the second optical coupling surface and covers thefirst and the second sidewalls.

This embodiment can facilitate coupling of the first core to the secondcore, because in this embodiment, the electromagnetic radiation can passnot only via the second and the first optical coupling surface but viathe second and the first sidewalls. The electromagnetic radiation can befurther confined within the medium.

In another embodiment, the set of alignment requirements furthercomprises: a length of an end portion of the first core beingimmediately above a portion of the second waveguide having its corecompletely covered by cladding and attached to the second core is biggerthan zero and less than a first length, the first length being less than10% of a length of the second core, wherein a length of the first coreis bigger than a sum of a length of the second core and the firstlength.

The embodiment can specify an advantageous alignment of the firstoptical coupling end segment with respect to the second optical couplingend segment in a lateral direction parallel to the longitudinalgeometric axis of symmetry of the first core and a longitudinalgeometric axis of symmetry of the second core.

FIG. 1 depicts a wafer prober 113 comprising the optical waveguide 104,105. The optical waveguide comprises an optical coupling end segment 104having the first optical coupling surface 110 being devoid of claddingand a segment 105 having its core completely covered by cladding. Merelyfor illustrative purposes, the first optical coupling end segment isdepicted as single unit 104 on the FIG. 1. Detailed structure of thefirst optical coupling end segment is depicted on the cross-section(FIG. 2). The first core 104′ of the first optical coupling end segment104 of the optical waveguide 104, 105 has a first optical couplingsurface 110 being devoid of cladding. The surface of the first corebeing opposite to the first optical coupling surface is covered bycladding 104A. First sidewalls 104L and 104R of the first core can be asoption devoid of cladding 104A′. The first optical waveguide 104, 105 isaffixed to a wafer prober card 106. The first core can have the samerectangular cross-section through-out its length. A point, where ageometrical axis of symmetry of the first core intersects a plane of thecross-section depicted on the FIG. 2, is marked by a dot 104S. Across-section of the first core matches a cross-section of the core ofthe segment 105 at an interface 104I, wherein these two cores areattached to each other.

The optical waveguide 104, 105 can flexible or rigid. It can be a glasswaveguide or made out of a least one of the following materials:silsesquioxane, poly-dimethylsiloxane, perfluoropolymer, acrylate,polyurethane, epoxy, and fluorinated polyimide.

The wafer prober comprises further a wafer holder 111 for holding asemiconductor wafer 100. The semiconductor wafer 100 comprises photoniccircuitry 103 and as option electronic circuitry. The photonic circuitrycomprises a second optical waveguide 101, 102 having the second opticalcoupling surface 112 being devoid of cladding and a segment 103 havingits core completely covered by cladding. Merely for illustrativepurposes, the second optical coupling end segment is depicted as singleunit 102 on the FIG. 1. Detailed structure of the second opticalcoupling end segment is depicted on the cross-section below. The secondcore 102′ of the second optical coupling end segment 102 of the opticalwaveguide 102, 103 has a second optical coupling surface 112 beingdevoid of cladding. The surface of the second core being opposite to thesecond optical coupling surface is covered by cladding 102A. Secondsidewalls 102L and 102R of the second core can be as option devoid ofcladding 102A′. The second optical coupling surface 112 is parallel to awafer surface. The second core can have a longitudinally tapered shape,wherein the second optical coupling surface of the second core isparallel to the surface of the second core covered by cladding 102A. Apoint, where a geometrical axis of symmetry of the second coreintersects a plane of the cross-section depicted on FIG. 2, is marked bya dot 102S. A cross-section of the second core matches a cross-sectionof the second core of the second optical coupling end segment 101 at aninterface 102I, wherein these two cores are attached to each other. Across-section of the second core at an end 102E being opposite to theinterface end 102I of the second core can be less than 100% and biggerthan 5% of the cross-section and the interface end 102I of the secondcore. The second core can have a length L2 in a direction of itsgeometrical axis of symmetry less than 3 mm, preferably less than 2 mm.The first core can have a length L4 in a direction of its geometricalaxis of symmetry bigger than the length of the second core. The secondoptical waveguide can have a Si core embedded in a SiO2 cladding.

The optical waveguide and the second optical waveguide can be singlemode optical waveguides. They can be configured to function atwavelengths in arrange of 1240-1380 nm or in a range 1450-1580 nm.

The optical waveguide 105, 104 can be configured to provide adiabaticcoupling to the second optical waveguide 101, 102 when a space betweenthe first optical coupling surface and the second coupling surface isfilled by a medium 107 having a refractive index less or equal to arefractive index of the first core. The medium can be liquid (e.g. wateror oil), a gel, or a solid (e.g. wax), which can fill the space in amolten state, while the measurements being performed when it issolidified. When the first side walls 104L, 104R and/or the second sidewalls 102L, 102R are devoid of cladding, then a contiguous volume of themedium 107 convers the sidewalls being devoid of cladding.

The wafer prober 113 can comprise means 108 for providing the medium asspecified above. The means 108 can be implemented in different ways, forinstance the means 108 can provide continuous circulation of liquidmedium 107 as it is customary in immersion lithography, alternativelythe means 108 can be configured to dispense the medium of the wafersurface before optical measurements and as option recollecting thedispensed medium after the optical measurements.

The optical waveguide 105, 104 is configured to provide adiabaticcoupling to the second optical waveguide 101, 102 when a set ofalignment requirements is fulfilled. The set of alignment requirementscomprises the following: the second optical coupling surface 112 isparallel to and faces the first optical coupling surface 110 and ageometrical plane comprising a longitudinal geometric axis of symmetryof the first core 104′ of the first optical coupling end segment 104 anda longitudinal geometric axis of symmetry of a second core 102′ of thesecond optical coupling end segment 102 is perpendicular to the wafersurface.

The set of alignment requirements can further comprise anotherrequirement when either the second coupling surface 112 is in contactwith the first optical coupling surface 110 or a distance D1 between thesecond optical coupling surface and the first optical coupling surfacebeing bigger than zero and less than 2 micrometers.

The set of alignment requirements can further specify alignment of thefirst optical coupling end segment 104 with respect to the secondoptical coupling end segment 102 in a lateral direction parallel to thelongitudinal geometric axis of symmetry of the first core 104′ and alongitudinal geometric axis of symmetry of the second core 102′. Thelength L2 of the second core 102′ is parallel to the length L4 of thefirst core 104′, wherein a projection of the second length L2 on thefirst length L4 is completely comprised in the first length. A length L1of an end portion of the first core 104′ being immediately above aportion of the second waveguide 101 having its core completely coveredby cladding and attached to the second core 102′ is bigger than zero andless than a first length, wherein the first length is less than 10% ofthe length L4 of the second core 102′, and the length L4 of the firstcore 104′ is bigger than a sum of a length L2 of the second core 102′and the first length. The length L1 of the end portion of the first coreis determined by an interval between an end point 104E of the first core104′ and a projection of the interface point 102I limiting the length ofthe second core 102′ on the length L4 of the first core 104′.

The wafer prober further comprises an alignment system configured toalign the optical waveguide 105, 104 with respect to the semiconductorwafer 100 according to the set of alignment requirements. The alimentsystem can comprise a motorized stage of the wafer holder 111 and or amotorized holder of the wafer probe card. The wafer prober can furthercomprise a computer system 109 configured to operate the alignmentsystem and/or means for providing the medium and/or means for conductingoptical/electrical measurements.

The optical waveguide can be used according to the following method forproviding an adiabatic coupling between the first optical coupling endsegment 104 of the optical waveguide 104, 105 and the second opticalcoupling end segment 102 of the second optical waveguide 101, 102 of aphotonic integrated circuit 103 on a semiconductor wafer 100. The methodcan be executed with or without the wafer prober 113. The methodcomprises the following: aligning the optical waveguide with respect tothe semiconductor wafer according to the set of the aforementionedalignment requirements, wherein the first optical segment comprises afirst optical coupling surface being devoid of cladding and the secondoptical coupling end segment comprises a second optical coupling surfacebeing devoid of cladding, wherein the second optical coupling surface isparallel to a wafer surface of the semiconductor wafer.

The method can further comprise the following steps when executed usingthe wafer prober: after the aligning the optical waveguide providing themedium 107 in between the first 110 and the second 112 optical couplingsurfaces as described above and performing a photonic/opticalmeasurement of a photonic circuitry 103 via the first 104, 105 and thesecond 101, 102 optical waveguide.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

What is claimed is:
 1. A wafer prober, the wafer prober comprising: anoptical waveguide, the optical waveguide comprising a first opticalcoupling end segment with a first optical coupling surface being devoidof cladding, the first optical coupling end segment being configured toprovide an adiabatic optical coupling to a second optical coupling endsegment of a second optical waveguide of a photonic integrated circuiton a semiconductor wafer when the optical waveguide is aligned withrespect to the semiconductor wafer according to a set of alignmentrequirements, the second optical coupling end segment comprising asecond optical coupling surface being devoid of cladding, the secondoptical coupling surface being parallel to a wafer surface of thesemiconductor wafer; and an alignment system configured to align theoptical waveguide with respect to the semiconductor wafer according tothe set of alignment requirements, wherein the set of alignmentrequirements comprises: the second optical coupling surface is parallelto and faces the first optical coupling surface; a geometrical planecomprising a longitudinal geometric axis of symmetry of a first core ofthe first optical coupling end segment and a longitudinal geometric axisof symmetry of a second core of the second optical coupling end segmentis perpendicular to the wafer surface; and a length of an end portion ofthe first core being immediately above a portion of the second waveguidehaving its core completely covered by cladding and attached to thesecond core is bigger than zero and less than a first length, the firstlength being less than 10% of a length of the second core, wherein alength of the first core is bigger than a sum of a length of the secondcore and the first length.
 2. The wafer prober of claim 1, the opticalwave guide and the second optical waveguide being single mode opticalwaveguides.
 3. The wafer prober of claim 1, the optical waveguide beingconfigured to function at a wavelength in a range of 1240-1380 nm, thesecond waveguide being configured to function at a wavelength in therange of 1240-1380 nm.
 4. The wafer prober of claim 1, the opticalwaveguide being configured to function at a wavelength in a range of1450-1580 nm, the second waveguide being configured to function at awavelength in the range of 1450-1580 nm.
 5. The wafer prober of claim 1,the optical waveguide is a polymer-based waveguide comprising at leastone of the following materials: silsesquioxane, poly-dimethylsiloxane,perfluoropolymer, acrylate, polyurethane, epoxy, and fluorinatedpolyimide.
 6. The wafer prober of claim 1, the optical waveguide being aglass waveguide.
 7. The wafer prober of claim 1, the second core havinga longitudinally tapered shape.
 8. The wafer prober of claim 1, thesecond core having a length shorter than 3 mm.
 9. The wafer prober ofclaim 1, the first core having the same cross-section throughout itslength.
 10. The wafer prober of claim 1, a length of the first corebeing longer than the length of the second core.
 11. The wafer prober ofclaim 1, the set of alignment requirements comprising: the secondoptical coupling surface being in contact with the first opticalcoupling surface.
 12. The wafer prober of claim 1, the set of alignmentrequirements comprises a distance between the second optical couplingsurface and the first optical coupling surface being bigger than zeroand less than 2 micrometers.
 13. The wafer prober of claim 1, the waferprober further comprising means for providing in a space between thefirst and the second optical coupling surface a medium having arefractive index less or equal to a refractive index of the first core,wherein the first optical coupling end segment is configured to providethe adiabatic optical coupling to the second optical coupling endsegment when the space between the first and the second optical couplingsurface is filled with the medium.
 14. The wafer prober of claim 1, thefirst core having first sidewalls being devoid of cladding, the firstsidewalls being adjacent to the first optical coupling surface.
 15. Thewafer prober of claim 14, the second core having second sidewalls beingdevoid of cladding, the second sidewalls being adjacent to the secondoptical coupling surface.
 16. The wafer prober of claim 15, wafer proberfurther comprising means for providing a contiguous volume of a mediumfilling a space between the first and the second optical couplingsurface and covering the first and the second sidewalls, the mediumhaving a refractive index less or equal to a refractive index of thefirst core, wherein the first optical coupling end segment is configuredto provide the adiabatic optical coupling to the second optical couplingend segment when the contiguous volume of the medium fills the spacebetween the first and the second optical coupling surface and covers thefirst and the second sidewalls.
 17. A method for providing an adiabaticcoupling between a first optical coupling end segment of an opticalwaveguide and a second optical coupling end segment of a second opticalwaveguide of a photonic integrated circuit on a semiconductor wafer, themethod comprising: aligning the optical waveguide with respect to thesemiconductor wafer according to a set of alignment requirements,wherein the first optical segment comprises a first optical couplingsurface being devoid of cladding and the second optical coupling endsegment comprises a second optical coupling surface being devoid ofcladding, wherein the second optical coupling surface is parallel to awafer surface of the semiconductor wafer; wherein the set of alignmentrequirements comprises: the second optical coupling surface is parallelto and faces the first optical coupling surface; a geometrical planecomprising a longitudinal geometric axis of symmetry of a first core ofthe first optical coupling end segment and a longitudinal geometric axisof symmetry of a second core of the second optical coupling end segmentis perpendicular to the wafer surface; and a length of an end portion ofthe first core being immediately above a portion of the second waveguidehaving its core completely covered by cladding and attached to thesecond core is bigger than zero and less than a first length, the firstlength being less than 10% of a length of the second core, wherein alength of the first core is bigger than a sum of a length of the secondcore and the first length.